JP5456789B2 - Glass substrate manufacturing apparatus and glass substrate manufacturing method - Google Patents

Description

  The present invention relates to a glass substrate manufacturing apparatus for manufacturing a glass substrate from molten glass and a glass manufacturing method for a glass substrate.

  Conventionally, a downdraw method has been used to manufacture a glass substrate from molten glass. In the downdraw method, molten glass is flowed on the wall surfaces on both sides of a wedge-shaped molded body extending in one direction, and two molten glass flows that flow down vertically along the wall surfaces on both sides are merged. Is used to form a glass substrate by forming molten glass into a strip-shaped glass having a predetermined thickness and cutting the glass on the strip into a desired size.

  When the molten glass flow having a certain width flowing down along the surface of the molded body is separated from the molded body, only the surface tension of the glass itself acts on the molten glass stream, so the width of the molten glass stream is narrow. I will try. For this reason, at least both ends in the width direction of the molten glass flow away from the compact are rapidly cooled to increase the viscosity so that the width of the molten glass flow is not reduced. For example, in the manufacture of a glass substrate for liquid crystal display, in the downdraw method, immediately after two molten glass streams are joined apart from the molded body, the end in the width direction of the molten glass is rapidly cooled from an upper space of 1200 to 1300 ° C. A method of moving to a lower space of a temperature atmosphere of about 400 to 700 ° C. or 600 to 700 ° C. can be used. In the lower space of about 400 to 700 ° C. or 600 to 700 ° C., a roller for rapidly cooling both ends in the width direction of the molten glass or a roller for extending the molten glass is provided. The molten glass is formed into a strip-shaped glass having a predetermined thickness by suppressing or stretching the width shrinkage of the molten glass due to rapid cooling of both ends in the width direction of the roller.

  When using such two spaces by partitioning one furnace chamber, a heat insulating plate is used to partition the two spaces. This heat insulating plate has low thermal conductivity so that heat is not conducted between the two spaces.

For example, there is known a glass plate manufacturing apparatus that includes a furnace wall that forms a furnace chamber, and a molded body that is disposed on the upper side of the furnace chamber, and that is drawn downward while cooling the sheet glass (Patent Literature). 1).
In this manufacturing apparatus, a substantially horizontal partition that separates the furnace chamber into an upper chamber (upper space) and a lower chamber (lower space) is disposed immediately below the molded body. Accordingly, the atmospheres of the upper and lower rooms can be prevented from affecting each other, and the temperatures of both atmospheres can be individually optimally controlled. At that time, ceramic fiber is used as a material for the heat insulating plate of the partition wall.

JP-A-2-149437

  However, when a ceramic fiber plate is used for the heat insulating plate, nonuniformity may be observed in the thickness of the strip glass due to the following reasons.

  The opposite surface of the gap through which the glass strip passes, which is made by the heat insulating plate, faces the glass ribbon, reflects the heat radiation emitted by the glass ribbon, and once absorbs the heat radiation emitted by the glass ribbon, then radiates again. And since it is made to absorb in strip | belt-shaped glass, it affects the temperature distribution of the width direction of strip | belt-shaped glass. In other words, the strip glass is affected by thermal radiation reflected by the opposing surface or thermal radiation (electromagnetic waves) absorbed by the opposing surface and radiated again, and affects the temperature distribution in the width direction. For example, ceramic fibers have a higher bubble content and lower thermal conductivity than alumina, which is the main component, in order to obtain a heat insulating effect. For example, when a ceramic fiber board in which such a ceramic fiber is hardened with a binder is used as a heat insulating plate, there is almost no effect of uniforming the temperature distribution of the heat insulating plate itself, and the amount of heat that the heat insulating plate can absorb from the molten glass is small. If there is a slight difference due to the location of the reflectance of the surface of the heat insulating plate due to a slight defect in the heat insulating plate, due to the difference, the heat radiation received from the opposite surface of the glass strip tends to be uneven, in other words, Thermal radiation that the opposite surface of the heat insulating plate absorbs in the belt-like glass tends to be non-uniform. In addition, when the temperature in the width direction of the strip glass has a distribution, if the strip glass gives thermal radiation different in the width direction to the opposing surface, the thermal radiation once absorbed by the opposing surface and radiated to the strip glass is also in the width direction. Different. In other words, when viewed from the strip glass, the effect of heat radiation received from the opposing surface of the heat insulating plate is likely to be non-uniform, so the temperature of the strip glass is difficult to equalize, resulting in a difference in viscosity in the width direction, resulting in thickness. Variation occurs.

  Therefore, in order to solve the conventional problems, the present invention maintains the heat insulation effect between the upper space and the lower space obtained by partitioning the furnace chamber with a heat insulating plate, and the thickness of the strip glass is not uniform. An object of the present invention is to provide a glass substrate manufacturing apparatus and a glass substrate manufacturing method capable of manufacturing a glass substrate by suppressing the above and stably manufacturing a glass strip.

One embodiment of the present invention is a glass substrate manufacturing apparatus that manufactures a glass substrate from molten glass using a downdraw method.
The device is
A furnace chamber surrounded by a furnace wall;
A molded body provided in the furnace chamber for molding a strip glass from molten glass;
A roller provided in the furnace chamber;
And a heat insulating plate using a heat insulating material that partitions the molded body and the roller into two different spaces.
In the furnace chamber, a slit-like gap is formed by the heat insulating plate for guiding the glass strip formed from the molded body to the space where the roller is located.
In the gap, a second material having a lower bubble content than the bubble content of the first material used for the heat insulating material is used at least on the facing surface of the heat insulating plate facing the strip glass. Alternatively, a second material having a higher thermal conductivity than the first material (provided that the bubble content is not 0%) is used for the opposing surface of the heat insulating plate.

For example, the heat insulating plate includes a plate member made of the first material in contact with the prism member,
The opposing surface of the heat insulating plate is a side surface of the prismatic member, and a plate surface of the heat insulating plate facing a space partitioned by the heat insulating plate is a plate surface of the plate member.
For example, the heat insulating plate includes a prism member made of the second material and a plate member made of the first material, and the prism member forms a frame that covers the periphery of the plate member.

Furthermore, another embodiment of the present invention is a method for manufacturing a glass substrate, in which a strip glass is manufactured from molten glass.
The manufacturing method is
Forming two molten glass streams on opposite wall surfaces of a molded body provided in a furnace chamber surrounded by the furnace wall;
Passing a glass strip formed by joining two molten glass streams through a slit-like gap formed by a heat insulating plate including a heat insulating material that partitions the furnace chamber.
At that time, in the step of passing the gap, in the gap through which the strip glass passes, the opposed surface of the heat insulating plate facing the strip glass is compared with the bubble content of the first material used for the heat insulating material. A second material having a low bubble content (however, the bubble content is excluding 0%) is used, and the facing surface provides a substantially uniform heat distribution in the width direction of the strip glass with respect to the strip glass. Or the opposing surface of the said heat insulation board reduces the deviation (difference of the maximum value of temperature, and the minimum value) of the temperature distribution which strip | belt-shaped glass holds in the width direction.

  The glass substrate manufacturing apparatus and the glass substrate manufacturing method described above are not uniform in thickness of the glass substrate while maintaining a heat insulating effect between the upper space and the lower space obtained by partitioning the furnace chamber with a heat insulating plate. Can be suppressed.

It is a figure explaining the flow of one Embodiment of the manufacturing method of the glass substrate of this invention. It is an external view of the apparatus which enforces a part of manufacturing method of the glass substrate of this embodiment. (A) is a schematic block diagram of the principal part of the manufacturing apparatus of the glass substrate which is embodiment of this invention, (b) is a perspective view of the molded object shown by (a). (A) is a block diagram of the heat insulation board shown by Fig.3 (a), (b) is sectional drawing along the A-A 'line | wire of the heat insulation board shown to (a). It is a figure which shows the deformation | transformation state of the conventional heat insulating board. (A), (b) is a figure which shows the cross-sectional structure of the modification of the heat insulating material used for the heat insulation board shown to Fig.3 (a). It is sectional drawing of the modification of the heat insulation board of this embodiment. It is sectional drawing of the other modification of the heat insulation board of this embodiment. It is a side view which shows the outline of a structure of the manufacturing apparatus of the glass substrate which is a modification of this embodiment. It is a front view which shows the outline of a structure of the manufacturing apparatus of the glass substrate which is a modification of this embodiment. It is a figure explaining the control system used for the manufacturing apparatus of the glass substrate which is a modification of this embodiment. It is a figure which shows the example of the heat insulation board of a prior art example.

  Hereinafter, the glass substrate manufacturing apparatus and the glass substrate manufacturing method of the present invention will be described in detail.

(Overall overview of glass substrate manufacturing method)
Drawing 1 is a figure explaining the flow of one embodiment of the manufacturing method of a glass substrate. FIG. 2 is an external view of an apparatus for carrying out a part of the glass substrate manufacturing method.
The glass plate manufacturing method of the present embodiment includes a melting step (ST1), a clarification step (ST2), a homogenization step (ST3), a supply step (ST4), a forming step (ST5), and a slow cooling step. (ST6) and a cutting process (ST7) are mainly included. In addition, a plurality of glass plates that have a grinding process, a polishing process, a cleaning process, an inspection process, a packing process, and the like and are stacked in the packing process are conveyed to a supplier.

The apparatus which performs a melting process (ST1)-a cutting process (ST7), as shown in FIG. 2, the melting apparatus 1 which has the melting tank 1a, the clarification tank 1b, and the stirring tank 1c, the shaping | molding apparatus 6, And a cutting device 8.
In the melting step (ST1), the glass raw material supplied into the melting tank 1a is heated and melted with a flame and an electric heater (not shown) to obtain molten glass.
The clarification step (ST2) is performed in the clarification tank 1b, and by heating the molten glass in the clarification tank 1b, oxygen and SO ₂ bubbles contained in the molten glass grow by the oxidation-reduction reaction of the clarifier. The air bubbles rise to the liquid surface and are released, or the gas components in the bubbles are absorbed into the molten glass, and the bubbles disappear.
In the homogenization step (ST3), the glass components are homogenized by stirring the molten glass in the stirring tank 1c supplied from the clarification tank 1b through the pipe 1d using a stirrer.
In the supply step (ST4), the molten glass is supplied to the molding apparatus 6 through the pipe 1e.
In the shaping | molding apparatus 6, a shaping | molding process (ST5) and a slow cooling process (ST6) are performed.
In the forming step (ST5), the molten glass is formed into a strip glass, and the strip glass that flows through the flow of the strip glass has a desired thickness. In the slow cooling step (ST6), cooling is performed so as not to cause warpage or plane distortion and to further increase the thermal contraction rate.
In a cutting process (ST7), in the cutting device 8, the glass substrate is obtained by cutting the strip glass supplied from the forming device 6 into a predetermined length. The cut glass substrate is further cut into a predetermined size, and then the glass end face is ground, polished, and cleaned. Further, after the presence of abnormal defects such as bubbles and striae is inspected, a glass substrate that has passed the inspection is packed as a final product.

  Fig.3 (a) is a schematic block diagram of the principal part of the manufacturing apparatus 10 of the glass substrate which is one Embodiment of this invention. The glass substrate manufacturing apparatus 10 and the glass substrate manufacturing method 10 using the glass substrate manufacturing apparatus 10 of the present embodiment are suitably applied to the manufacture of a glass substrate for a liquid crystal display or a glass substrate for a cover glass of a display. Moreover, it can also be used as a glass substrate for organic EL displays, a cover glass for housings such as portable terminal devices, a touch panel plate, a glass substrate for solar cells, and a cover glass. Moreover, it is suitable for the glass substrate for flat panel displays using p-Si * TFT (polysilicon TFT (Thin Film Transistor)). In particular, in a glass substrate for a liquid crystal display, when a plate thickness deviation that varies with respect to a target thickness occurs, an optical path difference occurs, and a light-dark difference occurs in a display image. For this reason, in the glass substrate for liquid crystal displays, the effect of the present invention that the thickness deviation can be suppressed becomes more remarkable.

A glass substrate manufacturing apparatus (hereinafter simply referred to as a glass manufacturing apparatus) 10 forms a glass strip from molten glass using a downdraw method, and manufactures a glass substrate through a cutting process. The glass manufacturing apparatus 10 includes a forming apparatus 6 and a cutting apparatus 8.
The glass manufacturing apparatus 10 includes a furnace chamber 12, a molded body 14, a roller 16, and a heat insulating plate 18. The direction perpendicular to the paper surface in FIG. 3A is the width direction of the belt-shaped glass, and the vertical direction in the paper surface in FIG. 1A is the height direction.

The furnace chamber 12 is a space surrounded by a furnace wall 12a assembled from refractory bricks, block-shaped electroformed pillar refractories, and the like. A molded body 14, a roller 16, and a heat insulating plate 18 are provided in the furnace chamber 12.
The molded body 14 includes a groove 14a opened upward, and the molten glass flows in the groove 14a. The molded body 14 is made of brick, for example. FIG. 3B is a perspective view of the molded body 14.

When the molten glass flows from the left side of FIG. 3B along the bowl-shaped path 15 in the direction of the arrow and flows to the right end of the groove 14a (not shown), the molten glass overflows from the upper wall portions on both sides of the groove 14a of the molded body 14. . The overflowing molten glass flows along the side wall surfaces 14b and 14c of the molded body 14. The two molten glass flows merge at the lowermost end 14 d of the molded body 14. As a result, the molten glass becomes band-shaped glass and is guided to the lower space where the roller 16 is located through the gap 19 formed by the heat insulating plate 18.
The roller 16 pulls the strip glass moved from the molded body 14 at a predetermined speed to form a strip glass having a predetermined thickness. The roller 16 is, for example, a long roller extending in the width direction of the strip glass. Alternatively, it may be two pairs of rollers that entrain and pull both ends in the width direction of the belt-shaped glass. The roller 16 also has a function of cooling both ends in the width direction of the strip glass. The roller having the cooling function may be provided upstream of the roller 16 separately from the roller 16.

The heat insulating plate 18 extends into the furnace chamber 12 from the same position in the height direction of the furnace wall 12a facing each other, and partitions the molded body 14 and the roller 16 into different upper and lower spaces. It is a pair of plate-like members using a heat insulating material. A pair of heat insulating plates 18 extending from the opposed furnace walls 12a are not in contact with each other, and a slit-like gap 19 extending in the width direction of the band glass is formed so that the molten band glass passes downward. ing. The reason why the furnace chamber 12 is divided into the upper space and the lower space by the heat insulating plate 18 is to perform temperature control in each of the upper space and the lower space so that the two spaces do not influence each other. For example, in the production of a glass substrate for a liquid crystal display, the upper space is held in a temperature atmosphere of 1200 to 1300 ° C. or higher, and the lower space is held in a temperature atmosphere of 400 to 700 ° C. (for example, 600 to 700 ° C.). Because.

For example, in the production of a glass substrate for a liquid crystal display, maintaining the atmosphere in the upper space at a temperature of 1200 to 1300 ° C. or higher causes the molten glass to be in a low-viscosity state and the molten glass spreads on the surface of the molded body 12. This is to create a “wet” state and prevent a reduction in the width of the molten glass flow on the surface of the molded body 14.
On the other hand, for example, in manufacturing a glass substrate for a liquid crystal display, the lower space is maintained in a temperature atmosphere of 400 to 700 ° C. (for example, 600 to 700 ° C.) immediately after the molten glass flow is merged by the molded body 14. This is because the shrinkage in the width direction of the molten glass due to the surface tension acting on the molten glass is suppressed by lowering the temperature to increase the viscosity.
The heat insulating plate 18 has durability against high heat of 1200 ° C. or higher in the upper space, and a material having low thermal conductivity is used as a heat insulating material for the heat insulating plate 18 in order to maintain the temperature difference between the upper space and the lower space. As a heat insulating material for the heat insulating plate 18, for example, a ceramic fiber board in which alumina fibers are hardened with a binder is preferably used. An alumina fiber is a type of ceramic fiber that is a fiber mainly composed of alumina (Al ₂ O ₃ ) and silica (SiO ₂ ). Alumina fiber contains 70 mass% or more of alumina and can be distinguished from other ceramic fibers containing 40 to 60 mass% of alumina. In addition, although the said fiber has an amorphous fiber and a crystalline fiber, a crystalline fiber is suitable at the point which is excellent in heat resistance.

Fig.4 (a) is a block diagram of the heat insulation board 18, FIG.4 (b) is AA 'shown to Fig.4 (a).
It is sectional drawing of the heat insulation board 18 along a line.
The heat insulating plate 18 is formed of a rectangular frame of the heat insulating plate 18 by hollow quadrangular columnar frame members 18a, 18b, 18c, and 18d, and ceramic fiber boards 18e to 18g in which alumina fibers are hardened by a binder in the frame. Is provided as a heat insulating main body. The size of the heat insulating plate 18 is, for example, 500 to 4000 mm on one side, and the shape of the surface having the largest area of the heat insulating plate 18 is, for example, a rectangular shape, and is rectangular or square.
The frame members 18a to 18d are fixed to each other by a joining member (not shown). The facing surface of the heat insulating plate 18 facing the strip glass is formed by the side surface of the frame member 18a. The side surface of the frame member 18a refers to a quadrangular surface standing from the bottom surface when the polygonal surface is referred to as the bottom surface in the quadrangular prism shape of the frame member 18. The heat insulating plate 18 is made of a material having a small variation in emissivity, a large heat capacity, and a high thermal conductivity.

For the frame members 18a to 18d, SiC or a material containing SiC as a main component (for example, a SiC sintered body) having a higher thermal conductivity than the alumina fibers of the ceramic fiber boards 18e to 18g is used. In addition, aluminum nitride ceramics can be used for the frame members 18a to 18d, and pure nickel, molybdenum or the like can be included as a component. In addition, the surface of these members can be coated or coated to improve the emissivity. Further, SiC or a material containing SiC as a main component (hereinafter referred to as SiC or the like) is a material having a low bubble content (for example, the bubble content is substantially 0) compared to the alumina fibers of the ceramic fiber boards 18e to 18g. Even if it is placed in the vicinity of a glass ribbon having a high temperature of 1200 ° C. or higher, it has durability. As the frame members 18a to 18d, in particular, those having a low bubble content among SiC and the like are preferable. For example, normal pressure sintered SiC having a bubble content of approximately 0 is preferable. In addition to SiC, a metal such as molybdenum covered with an oxide film may be used. Spaces in the rectangular column shape of the frame members 18a to 18d are filled with alumina fibers that are heat insulating materials.
Thus, the opposing surface of the heat insulating plate 18 that opposes the strip glass is a side surface of a quadrangular prism-shaped member, and the plate surface of the heat insulating plate facing the space partitioned by the heat insulating plate 18 is a plate member that is a ceramic fiber board. It is a plate surface. In addition, a board surface means the plane with the largest area among board | plate materials.
In the present embodiment, the frame members 18a to 18d are used. However, the frame member 18a may be used only in a portion corresponding to the facing surface of the heat insulating plate 18 that faces the belt-shaped glass in the gap 19.
The thickness of the plate forming each side surface of the hollow frame members 18a to 18d is preferably 5 to 10 mm. When the plate thickness exceeds 10 mm, the amount of heat insulating material to be filled in the hollow portions of the frame members 18a to 18d decreases, and the heat insulating effect as the heat insulating plate 18 decreases. On the other hand, when the plate thickness is less than 5 mm, the plate thickness When the thickness is small, the soaking effect is reduced, and it becomes difficult to uniformly radiate heat to the belt-like glass as will be described later. Therefore, it is preferable that the thickness of the plate forming the facing surface facing the strip glass of the frame member 18a is also 5 to 10 mm. In addition, with respect to the width of the heat insulating plate 18 existing in the furnace chamber 12 in the width (the length from the left end of the frame member 18a to the right end of the frame member 18b) of the heat insulating plate 18 in the horizontal direction in FIG. The ratio of the plate thickness of a member such as SiC provided on the facing surface of the heat insulating plate 18 facing the strip glass is preferably 0.01% to 5%, for example. When the ratio exceeds 5%, the amount of alumina fibers filled in the frame members 18a to 18d decreases, and the heat insulating effect as the heat insulating plate 18 decreases. On the other hand, when the ratio is less than 0.01%, soaking is performed. The effect is reduced, and it becomes difficult to uniformly radiate heat to the glass strip as will be described later.

As described above, the frame members 18a to 18d, in particular, the frame member 18a is a material having a lower bubble content than the heat insulating material such as alumina fiber of the heat insulating plate 18, has a small variation in emissivity, a large heat capacity, and a heat conduction. The reason why a material having a high rate is used is as follows.
That is, when the strip glass passes through the gap 19 formed by the pair of heat insulating plates 18, the temperature distribution in the width direction of the strip glass is affected by the heat radiation received by the strip glass from the facing surface of the heat insulating plate 18 facing the strip glass. The temperature distribution in the width direction of the band glass due to the heat received by the band glass by thermal radiation from the facing surface of the heat insulating plate 18 facing the band glass when the band glass passes through the gap 19 formed by the pair of heat insulating plates 18 Is affected).
A heat insulating material such as an alumina fiber has a porous structure containing air, and therefore does not have a large amount of heat that can be stored, and most of the heat radiation radiated from the strip glass is reflected as it is. For this reason, if there is a slight difference in reflection characteristics depending on the place on the surface of the heat insulating material, the influence reaches the glass surface that again absorbs the heat radiation. Therefore, a sufficient amount of heat can be stored on the opposing surface of the heat insulating plate 18, and even if there is a slight difference in reflection characteristics depending on the location of the surface of the heat insulating plate 18, the influence on the strip glass is relatively small. Thus, a material having a lower bubble content than alumina fiber is used. SiC or the like containing a material containing SiC as a main component can be suitably used for the facing surface of the heat insulating plate 18 because the bubble content is lower than that of the alumina fiber.
In addition, a material having high thermal conductivity is used for the frame members 18a to 18d so as to have a function of mitigating nonuniformity of heat radiation received along the width direction of the strip glass. In particular, even if there is a temperature difference between the opposing surfaces of the heat insulating plate 18 facing the belt-like glass, the opposite surface of the heat insulating plate 18 has heat compared to the heat insulating material in order to reduce the temperature difference along the width direction. A material with high conductivity is used. SiC or the like has a higher thermal conductivity than that of the alumina fiber, and has high-temperature durability of 1200 ° C. or higher. Therefore, SiC or the like can be suitably used for the facing surface of the heat insulating plate 18. Due to the high thermal conductivity of the opposing surface of the heat insulating plate 18, mutual heat exchange occurs when the glass strip passes through the vicinity of the heat insulating plate 18 even if the opposing glass strips originally have a temperature distribution in the width direction. Accordingly, the temperature distribution in the width direction can be improved to some extent. In other words, in the gap 19 through which the strip glass passes, the opposing surface of the heat insulating plate 18 facing the strip glass gives a substantially uniform heat distribution to the strip glass, thereby causing a temperature distribution deviation (temperature) in the width direction. The difference between the highest and lowest values).
In addition to SiC, molybdenum having an oxide film formed on the surface may be used. In addition, SiC has higher surface smoothness, higher rigidity, and higher flatness as a structure (uniformity in distance in the width direction between opposing glasses) than heat insulating materials such as alumina fibers. It is also easy to keep. Therefore, as described above, the effect of making the temperature of the facing surface facing the strip glass constant along the width direction and suppressing nonuniformity of heat radiation radiated from the facing surface facing the strip glass is even higher. Become. Thereby, the dispersion | variation in the viscosity which arises in the width direction of strip | belt-shaped glass can be suppressed, and the thickness of strip | belt-shaped glass is also equalized.

In the present embodiment, an example in which SiC is used as the material of the frame members 18a to 18d has been described, but the thermal conductivity at the temperature of the upper space is 25 W / m · K or more, more preferably 45 W / m · A material having a thermal conductivity of K or higher, particularly preferably 50 W / m · K or higher is preferable. Therefore, as the material of the frame members 18a to 18d, the thermal conductivity at the temperature of the upper space is 25 to 200 W / m · K, more preferably 45 to 200 W / m · K, and particularly preferably 50 to 200 W / m. A material having a thermal conductivity of K is preferable. Moreover, as a material of the frame members 18a to 18d, it is preferable to apply a material having a high emissivity at the temperature of the upper space as compared with the heat insulating material. For example, the emissivity of the material of the frame members 18a to 18d is preferably 0.8 to 1, and more preferably 0.95 to 1. Moreover, in order to suppress the dispersion | variation in the temperature distribution of strip | belt-shaped glass, the bubble content rate of the material of frame member 18a-18d is 0-15%, Preferably it is 0-5%, More preferably, it is 0-2.5%. It is.
On the other hand, as the heat insulating material, in addition to the alumina fiber, other ceramic fiber containing 40 to 60% by mass of alumina or microtherm (trade name, manufactured by Nippon Microtherm Co., Ltd.) can be used. The heat insulating material is not limited to the above materials, and the thermal conductivity at the temperature of the upper space is preferably 1 W / m · K or less, preferably 0.5 W / m · K or less, more preferably 0.8. The material may be 3 W / m · K or less, more preferably 0.1 W / m · K or less, and particularly preferably 0.05 W / m · K or less. In other words, the thermal conductivity of the heat insulating material at the temperature of the upper space is preferably 0 to 1 W / m · K, preferably 0 to 0.5 W / m · K, more preferably 0 to 0.3 W / m · K. K, more preferably 0 to 0.1 W / m · K, particularly preferably 0 to 0.05 W / m · K or less. Moreover, in order to acquire the heat insulation effect, the bubble content rate of a heat insulating material is 20 to 100%, Preferably it is 35 to 100%, More preferably, it is 40 to 100%.

Moreover, in order to control temperature independently in the upper space and lower space in the furnace chamber 12, it is preferable that the thickness of the heat insulating plate 18 is thicker. However, if the thickness of the heat insulating plate 18 becomes too thick, it may be difficult to install a heater or the like for heating the molded body 14 in the vicinity of the molded body 14. Therefore, the thickness of the heat insulating plate 18 is preferably 30 mm to 250 mm, more preferably 50 mm to 200 mm, and still more preferably 100 mm to 200 mm.
The heat resistance of the heat insulating plate 18 is preferably 0.2 m ² · K / W or more, more preferably 0.4 m ² · K / W or more, and further preferably 0.5 m ² · K / W or more. Good. The thermal resistance can be adjusted by changing the material and thickness of the heat insulating plate.
By using the heat insulating plate 18 having the above heat resistance, the heat insulating effect is improved, the energy efficiency of cooling or heating in the upper space and the lower space is improved, and the cost can be reduced.

For thermal conductivity measurement, fine ceramics laser flash method thermal conductivity test method (JIS R 1611-1997), electrical insulator ceramic material test method (JIS C 2141-1992), thermal diffusivity A known method such as a measurement method (ASTM E 1461) can be used.
The bubble content can be calculated by {1- (bulk density / true density) × 100}. The thermal resistance can be calculated according to the thermal resistance = thickness / thermal conductivity using the thermal conductivity. The emissivity can be measured by a radiation thermometer.

  Moreover, the shape of the heat insulation board 18 is not limited to a rectangular parallelepiped. For example, the heat insulating plate 18 is preferably installed in the very vicinity of the molded body 14 so that the glass strip formed in the molded body 14 can be quickly cooled to increase the viscosity. At this time, the heat insulating plate 18 is formed of the frame member 18a of the heat insulating plate 18 in order to approach the lower inclined surface of the formed body 14 in a wide range so that the heat insulating effect in the upper space and the lower space is enhanced. The upper corner of the surface facing (molten glass) is preferably chamfered in a direction substantially parallel to the lower inclined surface of the molded body 14. In other words, the upper part of the surface of the heat insulating plate 18 that faces the formed body or the strip-shaped glass is chamfered so that the distance between the planes between the heat insulating plate 18 and the formed body 14 or the molten glass is substantially constant. Preferably there is. By setting the heat insulating plate 18 to the chamfered shape, the heat insulating plate 18 can be brought close to the molten glass in a wide range without contacting the molten glass. As a result, it is possible to suppress the influence of thermal radiation from the heat insulating plate 18 to the molten glass from being varied in the flow direction of the molten glass.

  FIG. 5 is a view showing a deformed state of the conventional heat insulating plate 118. The conventional heat insulating plate 118 is composed of a ceramic fiber board 118 in which alumina fibers are hardened with a binder without using the frame members 18a to 18d. When the heat insulating plate 118 is used for a long time to partition the space in the furnace chamber, the side facing the upper space on the high temperature side gradually contracts with time due to the binder for hardening the alumina fiber, and the band shape In the heat insulating plate 118 that forms a gap through which glass passes, a “warp” that deforms into a concave shape (convex shape with respect to the lower space) with respect to the upper space occurs (see FIG. 5). On the other hand, since the molded body 114 is provided immediately above the heat insulating plate 118, the position in the height direction of the central portion of the facing surface of the heat insulating plate 18 facing the band-shaped glass (the flowing direction of the molten glass or the band-shaped glass) is It is lower than the position in the height direction of the end portion of the opposing surface of the heat insulating plate 18.

Originally, the heat insulating plate 118 is close to the glass bonding line at the lower end of the molded body 114 in the height direction and at a certain distance, so that the molten glass ribbon is cooled early and uniformly, and a desired width is obtained. It is preferable in terms of ensuring sufficient. If the position of the heat insulating plate 118 is too low with respect to the glass joining line at the lower end of the molded body 114, the width of the strip glass will be greatly reduced. If it is too high, the viscosity of the molten glass will be too high, and the molten glass will not be joined well at the glass joining line.
For this reason, the occurrence of “warping” in the heat insulating plate 118 as shown in FIG. 5 is not preferable in that the thickness of the strip glass and the bonding characteristics change with time as the strip glass is manufactured. A member using SiC or the like has high rigidity, and even if deformation due to an expansion difference based on a temperature difference occurs, the amount of deformation does not change greatly over time unlike a ceramic fiber board.
Furthermore, a member using SiC or the like is excellent in oxidation resistance in a high temperature and oxidizing atmosphere, has high surface smoothness, and extremely little variation in smoothness depending on location.
For this reason, even if the facing surface using SiC or the like is arranged in the vicinity of a glass ribbon having a high temperature of 1200 ° C. or higher, the quality of the glass ribbon or glass substrate to be formed (for example, glass ribbon due to variation in the width direction of the temperature distribution) And variation in the thickness of the glass substrate).
In addition, the curvature amount of the heat insulation board 118 mentioned above increases, so that the magnitude | size of a heat insulation board or the glass substrate to manufacture is large. As the amount of warpage increases, the glass substrate forming width changes, and as a result, the cooling conditions at both ends in the width direction of the belt-like glass change. The quality of the substrate will deteriorate.

On the other hand, the opposing surface of the heat insulating plate 18 formed by the heat insulating plate 18 reflects heat radiation (electromagnetic waves such as infrared rays) radiated by the molten glass or radiates the heat radiation once absorbed toward the glass surface again. This thermal radiation (electromagnetic wave) affects the molten glass temperature. This heat transfer by radiation is basically unaffected by the mutual distance, but convection heat transfer due to the air flow existing there also contributes to the heat exchange between the two, so between the molten glass and the facing surface It is preferable that the distance is uniform in the width direction of the molten glass (or the direction along the gap) as a result of uniforming the temperature of the strip glass and suppressing variation in the thickness of the strip glass.
In addition, if there is uneven unevenness on the facing surface of the heat insulating plate 18, the heat radiation in the normal direction of the reflecting surface of the facing surface that reflects the heat radiation (electromagnetic wave) emitted from the strip glass becomes non-uniform. As a result, the heat that is received becomes uneven in the width direction, and as a result, the temperature distribution in the width direction of the strip glass becomes uneven. This influence is greater as the emissivity of the opposing surface of the heat insulating plate 18 is lower. When the emissivity of the opposing surface of the heat insulating plate 18 is high, heat is radiated relatively uniformly in all directions, whereas when the emissivity is low, it is difficult to absorb the heat of the molten glass, and uneven unevenness of the opposing surface. Depending on the state, it is possible that the thermal energy of the heat radiation (electromagnetic wave) emitted from the glass strip in a specific direction is reflected intensively. For this reason, the heat which a strip glass receives becomes non-uniform | heterogenous in the width direction, As a result, the temperature distribution of the width direction of a strip | belt glass becomes non-uniform.
From the above, in order to suppress the non-uniformity of the temperature distribution in the width direction of the band-shaped glass and, in turn, to suppress the non-uniformity in the width direction of the thickness of the band-shaped glass and the glass substrate, the surface of the facing surface of the heat insulating plate 18 is It is preferable that there is no unevenness, or even if there is unevenness, the unevenness is uniform, or the emissivity of the opposing surface is high.
Since the ceramic fiber board used for the conventional heat insulating plate 118 has a porous structure including air as a heat insulating material, it is difficult to make the surface of the ceramic fiber board uniform without unevenness. In addition, since the ceramic fiber board has extremely low hardness, the opposing surface may be locally uneven or scratched when installed in the furnace chamber. As a result, a non-uniform temperature distribution is created in the strip glass, and there is a case where a distribution is created in the thickness of the strip glass formed by stretching the strip glass and the glass substrate obtained thereafter.

On the other hand, members such as SiC have higher hardness than ceramic fiber boards and have a relatively smooth and uniform surface, so that the temperature distribution of the strip glass is not deteriorated (the temperature distribution in the strip glass). Therefore, an unnecessary distribution is not created in the thickness of the glass strip and the glass substrate formed by stretching the glass strip.
Alternatively, a member such as SiC has a higher emissivity than a ceramic fiber board, and once absorbed heat diffuses quickly inside the member and radiates relatively uniformly (in all directions). Even if there are slight irregularities on the opposing surfaces, the variation in heat received by the strip glass is smaller than that of the ceramic fiber board.
For this reason, when using a member such as SiC on the opposing surface of the heat insulating plate 18, it is possible to stably manufacture a strip-shaped glass and a glass substrate having a predetermined thickness as compared with the case where a conventional ceramic fiber board is used for the heat insulating plate. it can.

By forming the opposing surface of the heat insulating material 18 by the side surface of one frame member 18a as in the present embodiment, there is no seam between the members that become thermal singularities, so the temperature distribution on the opposing surface and the glass strip are given. Variation in heat can be suppressed. The board made of a heat insulating material surrounded by the frame members 18a to 18d has two seams because it is composed of three ceramic fiber boards 18e to 18g, but these seams are separated from the strip glass. The effect is small and does not become a thermal singularity that has a local effect on the temperature of molten glass or strip glass.
Further, by using a hollow quadrangular prism member for the frame members 18a to 18d, the hollow portion can be filled with a heat insulating material such as alumina fiber. For this reason, even if it uses material with high heat conductivity compared with heat insulating materials, such as an alumina fiber, for the frame members 18a-18d, the heat insulation effect of the heat insulation board 18 is maintainable. Even in the case where the hollow portions of the frame members 18a to 18d are not filled with the heat insulating material, the air in the hollow portions fulfills a heat insulating function to some extent. However, the temperature difference between the part facing the upper space and the part facing the lower space across the hollow part becomes 600 ° C. or more, and heat exchange occurs due to air convection or heat radiation in the hollow part. Therefore, it is more preferable to fill the hollow portion with a heat insulating material such as alumina fiber. By filling the hollow part with a heat insulating material such as alumina fiber, the hollow part is separated into an extremely large number of rooms, air can not move between rooms, and heat radiation is also blocked, so the heat insulation function can be effectively performed. Fulfill.

  Furthermore, by using the hollow frame members 18a to 18d for the heat insulating plate 18, it is possible to configure a light plate having a large second moment of section with the same weight as compared with a solid material, light and having high mechanical strength.

  Although the heat insulation board 18 of this embodiment was comprised with the four frame members 18a-18d, it is not limited to this. A frame member may be used on at least the facing surface of the heat insulating plate 18 facing the strip glass. In addition to the four frame members 18a to 18d, frame members of the same shape and material may be used as the reinforcing beam for the frame. Further, the frame members 18a to 18d may not be a quadrangular prism member, but may be a triangular prism member or a polygonal prism member. Further, the frame members 18a to 18d forming the rectangular frame of the heat insulating plate 18 do not necessarily need to be frames, and at least a portion corresponding to the facing surface of the heat insulating plate 18 facing the strip glass in the gap 19 is provided with a heat insulating material. The problem of the present invention can be solved by using a material having a low bubble content or a material having a high thermal conductivity. For example, the frame member 18a may be a plate-shaped or L-shaped member.

  By using the heat insulating plate 18 of the present embodiment, it is possible to stably manufacture a strip glass and a glass substrate having a certain thickness and certain quality. In addition, a plurality of ceramic fiber boards may be provided without gaps so as to be surrounded by the frame members 18a to 18d, so that the size is larger and more expensive than the standard size so as not to make a seam on the opposing surface of the heat insulating plate. The ceramic fiber board is no longer used. For this reason, the cost of the manufacturing apparatus of a glass substrate reduces. Further, since a frame member such as SiC having high hardness is used, there is less risk of scratching the opposing surface or creating irregularities when the frame member is installed, and workability is improved.

When manufacturing strip glass using such a glass manufacturing apparatus 10, first, two molten glass is provided on the mutually opposing wall surfaces 14b and 14c of the molded body 14 provided in the furnace chamber 12 surrounded by the furnace wall 12a. Form a flow.
Next, the glass strip formed by joining two molten glass streams is passed through a slit-like gap 19 formed by a heat insulating plate 18 that partitions the inside of the furnace chamber 12.
Thereafter, the glass strip is stretched using rollers 16 provided in a space different from the molded body 14 partitioned by the heat insulating plate 18 in the furnace chamber 12, or both ends in the width direction of the glass strip are cooled. Thereby, a strip-shaped glass having a predetermined thickness is produced.
In the slit-shaped gap 19 through which the strip glass passes, the opposing surface of the heat insulating plate 18 facing the strip glass has a high thermal conductivity and is smooth and uniform compared to the thermal conductivity of the heat insulating material used for the heat insulating plate 18. A material with a smooth surface is used. Thereby, for the reasons described above, it is possible to stably manufacture a strip-shaped glass and a glass substrate having a predetermined thickness as compared with the case where a conventional ceramic fiber board is used as a heat insulating plate.

In addition, the glass substrate manufactured by this embodiment and the following modified example has the following compositions, for example. The alkali-free glass having the following composition is suitable for a glass substrate for flat panel display, and particularly suitable for a glass substrate for liquid crystal display and a glass substrate for organic EL display.
(A) SiO ₂ : 50 to 70% by mass,
(B) B ₂ O ₃ : 5 to 18% by mass,
(C) Al ₂ O ₃ : 10 to 25% by mass,
(D) MgO: 0 to 10% by mass,
(E) CaO: 0 to 20% by mass,
(F) SrO: 0 to 20% by mass,
(O) BaO: 0 to 10% by mass,
(P) RO: Total content of 5 to 20% by mass (wherein R is a component contained among Mg, Ca, Sr and Ba).
Moreover, although it was set as the alkali free glass in the above, the glass substrate may contain a trace amount of alkali. When containing alkali,
(Q) R ′ ₂ O: The total content is more than 0.20% by mass and 2.0% by mass or less (where R ′ is a component contained among Li, Na, and K). Incidentally, Li ₂ O, without Na ₂ O is allowed to contain, in the component, preferably eluted from the glass to contain hardly K ₂ O that is degraded most characteristics of the TFT.
(R) It is preferable to contain 0.05 to 1.5% by mass in total of at least one metal oxide selected from tin oxide, iron oxide and cerium oxide as a fining agent.
Depending on the composition of the glass, molding is possible even when the temperature of the upper space is less than 1200 ° C. In this case, the heat insulating material is not necessarily required to have the heat resistance as that of the crystalline alumina fiber, and other heat insulating materials such as amorphous alumina fiber and ceramic fiber can be used.

Moreover, the glass composition of the other glass substrate manufactured by this embodiment can mention the following, for example. By setting it as the composition shown below, the strain point temperature (the temperature of the glass having a glass viscosity log of 14.5) in the strip glass can be increased, and the amount of heat shrinkage during the heat treatment can be further reduced. Therefore, it is suitable for a glass substrate for liquid crystal display and a glass substrate for organic EL display, and is particularly suitable for a TFT to which p-Si · TFT is applied. A liquid crystal display or an organic EL display to which p-Si • TFT is applied is required to have high-definition characteristics. Therefore, in the production of a glass substrate for liquid crystal display and a glass substrate for organic EL display to which p-Si • TFT is applied, the effect of suppressing the plate thickness deviation in this embodiment becomes remarkable.
SiO _2: 57~75% by weight,
Al ₂ O ₃ : 8 to 25% by mass,
B ₂ O ₃ : 3% by mass or more and less than 11% by mass,
CaO: 0 to 20% by mass,
MgO: 0 to 15% by mass,
An alkali-free glass having a strain point of 680 ° C. or higher.

At this time, if the composition is determined so as to satisfy the following mathematical formula, the glass substrate for p-Si · TFT is more suitable.
SrO + BaO: 0 to 3.3% by mass,
CaO / RO: 0.65 or more (where R is a component contained among Mg, Ca, Sr and Ba),
SiO ₂ + Al ₂ O ₃ : 79% by mass or more,
CaO / B ₂ O ₃ : 0.6 or more In addition, although it was set as the alkali free glass in the above, the glass substrate may contain a trace amount of alkali. When the alkali is contained, it is preferable that the total content of R ′ ₂ O exceeds 0.20 mass% and is 2.0 mass% or less (where R ′ is a component contained among Li, Na, and K). Incidentally, Li ₂ O, without Na ₂ O is allowed to contain, in the component, preferably eluted from the glass to contain hardly K ₂ O that is degraded most characteristics of the TFT. Also includes 0.05 to 1.5 wt% of a clarifying agent in total, it is preferably free of _{As 2 O 3, Sb 2 O} 3 and PbO substantially. As the fining agent, it is particularly preferable to contain SnO ₂ . Moreover, in order to make melting of glass easy, it is more preferable that content of the iron oxide in glass is 0.01-0.2 mass% from a viewpoint of reducing a specific resistance.

  The thickness of the glass substrate manufactured in this embodiment is, for example, 0.1 mm to 1.5 mm. Preferably it is 0.1-1.2 mm, More preferably, it is 0.3-1.0 mm, More preferably, it is 0.3-0.8 mm, Most preferably, it is 0.3-0.5 mm.

  The length in the width direction of the glass substrate of the present embodiment is, for example, 500 mm to 3500 mm, preferably 1000 mm to 3500 mm, and more preferably 2000 mm to 3500 mm. On the other hand, the length of the glass substrate in the vertical direction is, for example, 500 mm to 3500 mm, preferably 1000 mm to 3500 mm, and more preferably 2000 mm to 3500 mm. As described above, the larger the size of the glass substrate and the larger the size of the heat insulating plate 118, the larger the “warp” amount of the heat insulating plate 118, and the characteristics of the plate thickness deviation and the warp and strain of the strip glass or glass substrate. Will get worse. That is, the effect of this embodiment becomes more remarkable in the glass substrate whose length in the width direction of the glass substrate is 2000 mm or more.

  The plate | board thickness deviation of the glass substrate manufactured in this embodiment becomes like this. Preferably it is less than 0-25 micrometers, More preferably, it is 0-23 micrometers, More preferably, it is 0-15 micrometers.

(Modification 1)
FIGS. 6A and 6B are views showing a cross-sectional configuration of a heat insulating main body 18 h showing a modification of the ceramic fiber boards 18 e to 18 g surrounded by the frame member 18 of the heat insulating plate 18.
The heat insulating main body 18h shown in FIG. 6A has a configuration in which a material with high heat insulation is arranged at the center and the periphery thereof is covered with a material with high temperature durability. For example, microtherm (trade name, manufactured by Nippon Microtherm Co., Ltd.) is used as a material having high heat insulation, and ceramic fiber including alumina fiber is used as a material having high temperature durability.
Or you may comprise with the multiple types of material laminated | stacked in layer shape like the heat insulation main-body part 18h shown in FIG.6 (b). In this case, a material having high temperature durability is used on the side in contact with the upper space in the high temperature atmosphere, and a material having excellent heat insulating properties is used on the side in contact with the lower space, although the heat resistant temperature is inferior. In the case of the three-layer structure shown in FIG. 6B, a ceramic fiber having a high alumina content is used as the layer in contact with the upper space, and the alumina content is higher in the intermediate layer. A ceramic fiber lower than the ceramic fiber used for the layer in contact with the ceramic is used, and the layer in contact with the lower space is the ceramic fiber having the lowest alumina content in each layer, or microtherm (manufactured by Nihon Microtherm) Product name) is used.
Thus, the heat insulation main-body part can improve a heat insulation effect by comprising combining a plurality of kinds of heat insulation materials.

(Modification 2)
FIG. 7 is a cross-sectional view of the vicinity of a gap 19 between a pair of heat insulating plates 18 provided with a molten glass ribbon sandwiched therebetween.
As shown in FIG. 7, on the opposite surface side of the frame member 18a, a hollow square column member 20 having a smaller cross section than the frame member 18a is provided along the gap 19 as a single member (without a joint). Yes. The material of the member 20 is the same material as that of the frame member 18a. The member 20 is fixed to the frame member 18a so that the surface in contact with the lower space is flush with the surface in contact with the lower space of the frame member 18a. The hollow portion of the member 20 is filled with a heat insulating material 22 such as an alumina fiber, like the frame member 18a. With such a configuration, the width of the first opening end facing the upper space of the gap through which the strip glass passes is wider than that of the second opening end facing the lower space (the first opening). The opening end has a narrower gap than the second opening end).
In this modification, the member 20 is provided in one stage on the frame member 18a. However, another member having the same shape as the member 20 but having a small size may be provided in multiple stages on the opposing surface of the member 20.
The member 20 of the present modification has a quadrangular prism shape, but is not limited to a quadrangular prism shape, and may be a member having another shape such as a triangular prism. The member 20 and other members may be combined so that the gap becomes narrower toward at least the lower space.

  The reason why the widths of the open ends of the gaps are made different in this way is to widen the open end facing the upper space and bring them closer to the molded body 14. Since the lower part of the molded body 14 is an inclined surface, unless the gap between the open ends facing the upper space is made wider than the gap facing the lower space, the heat insulating plate is placed at a higher position with respect to the glass flow. I ca n’t get close. As described above, the gap between the heat insulating plates 18 and the molded body 14 are brought close to the flow of the strip glass at a certain level so that the width of the strip glass is sufficiently wide as long as the joining at both ends of the strip glass is not unstable. This is to ensure it widely. In particular, by providing the frame member 18a with the member 20 having a small cross section and the same material as the frame member 18a, the heat insulating plate 18 can be brought closer to the molded body 14 at a higher position with respect to the glass flow. Since the hollow portion of the member 20 is filled with the heat insulating material 22 like the member 18a, the heat insulating function as the heat insulating plate 18 can be achieved.

(Modification 3)
FIGS. 8A and 8B are cross-sectional views in the vicinity of a gap 19 between a pair of heat insulating plates 18 provided with a glass ribbon in a molten state interposed therebetween.
As shown in FIG. 8A, the shape of the heat insulating plate 18 is a rectangular column having a hollow, and the tube 23 is provided on the surface farthest from the strip glass among the surfaces constituting the rectangular column. Yes. An air supply source (not shown) is connected to the tube 23. Moreover, the material similar to the said frame member 18a is used for the member 18i which forms the opposing surface which is the nearest to strip | belt glass among the surfaces which comprise the said square pillar, and opposes strip | belt-shaped glass. The tube 23 can flow air having a desired temperature into the hollow provided in the heat insulating plate 18.
In this modification, the upper and lower spaces are maintained at a desired temperature by using the air flowing from the tube 23 as the heat insulating material 18n. In addition, the surface which forms the upper space side or the lower space side among the heat insulating plates 18 may be provided with an opening through which air introduced from the tube 23 passes. Or the discharge tube which discharges | emits the hollow air of a heat insulation board outside may be provided. Here, the temperature, flow rate or pressure of the air flowing in from the tube 23 can be appropriately changed.
As shown in FIG. 8 (b), the heat insulating plate 18 includes a member 18i using the same material as the frame member 18a described above and plate-shaped heat insulating materials 18j, 18k, and 18m. You may make it comprise a prism. Thereby, compared with the case mentioned above, the heat insulation effect can be improved. The member 18i may be L-shaped with the upper space side as the bottom surface.

(Modification 4)
This modification uses the above-described heat insulating plate 18 in the glass manufacturing apparatus 10 and further suppresses the above-described plate thickness deviation more efficiently in the furnace manufacturing space (outside the furnace chamber) and the furnace in the glass manufacturing apparatus 10. It is an example of controlling the pressure difference with the internal space (furnace chamber).
9 and 10 show a glass manufacturing apparatus 10 that performs a forming process and a slow cooling process, and a cutting apparatus 8 that performs a cutting process. The glass manufacturing apparatus 10 is partitioned by a furnace wall 12a and is connected to a furnace external space (furnace). Outside the chamber) and the furnace interior space (inside the furnace chamber). 9 and 10 are diagrams mainly showing the configuration of the glass manufacturing apparatus 10, FIG. 9 mainly shows a schematic side view of the glass manufacturing apparatus 10, and FIG. 10 is a schematic front view of the glass manufacturing apparatus 10. Indicates.

  The interior space (furnace chamber) of the molding furnace 80 that performs the molding process and the slow cooling furnace 50 that performs the slow cooling process is surrounded by a furnace wall 12a made of a refractory material such as a refractory brick. The molding furnace 80 is provided vertically above the slow cooling furnace 50. The molding furnace 80 and the slow cooling furnace 50 are collectively referred to as a furnace. In the furnace inner space surrounded by the furnace wall 12a of the furnace, the molded body 14, the heat insulating plate 18 as an atmosphere partition member, the roller 16, the cooling unit 30, the transport rollers 32a to 32h, and the pressure sensors 60 and 62a. To 62c (see FIG. 10) are provided.

  Below the cooling unit 30, transport rollers 32a to 32h are provided at predetermined intervals, and pull the strip glass downward. The space below the cooling unit 30 is a furnace internal space partitioned by the furnace wall 12a. Each of the transport rollers 32a to 32h has a pair of rollers, and is provided at both end portions in the width direction of the strip glass so as to sandwich both sides of the strip glass.

  A pressure sensor 60 (see FIG. 10) for measuring the pressure in the furnace internal space is provided in the furnace internal space of the molding furnace 80 partitioned by the furnace wall 12a. The pressure sensor 60 is provided at the same position in the height direction (vertically upward direction) as the molded body 14. Pressure sensors 62 a to 62 c (see FIG. 10) are provided in the furnace internal space of the slow cooling furnace 50.

  On the other hand, on the outside of the furnace wall 12a of the molding furnace 80, a space (space outside the furnace chamber 12) partitioned by the partition wall of the building B with respect to the atmospheric pressure atmosphere by the partition wall, that is, the furnace exterior space S1, S2, S3a. To S3c are provided. Each of these spaces is delimited by floor surfaces 41, 42, 43a to 43c in the height direction. That is, the glass manufacturing apparatus 10 is provided in a building B having a plurality of floors, and furnace external spaces (partial spaces) S1, S2, S3a to S3c divided into a plurality of floor surfaces are provided on each floor. Further, a space S4 (cutting space) partitioned by walls on the floor surface 44 is provided below the furnace external space S3c. In the space S4, the strip glass G is cut using the cutting device 8 to obtain a glass substrate. The furnace wall 12a is not provided in the space S4. The air pressure in these spaces is adjusted by blowers 52, 53, 54a, 54b, 54c, and 55, which will be described later.

The furnace outside space S1 is a space vertically above the position in the height direction of the molded body 14, and a pressure sensor 45 that measures the atmospheric pressure in the furnace outside space is provided in the furnace outside space S1.
The furnace exterior space S2 is a space provided on the floor surface 42, and the molded body 14 is disposed in the furnace interior space corresponding to this space. Further, a pressure sensor 46 for measuring the atmospheric pressure in the furnace external space S2 is provided in the furnace external space S2. In the furnace internal space surrounded by the furnace wall 12a, a pressure sensor 60 for measuring the pressure in the furnace internal space is provided at the same position in the height direction of the pressure sensor 46 (see FIG. 10).
The furnace outer spaces S3a to S3c are spaces provided in the order of the furnace outer spaces S3a to 3c from the higher side in the height direction below the furnace outer space S2. The furnace outer spaces S3a to 3c are provided on the floor surfaces 43a to 43c. Further, pressure sensors 47a to 47c for measuring the atmospheric pressure in the furnace external spaces 3a to 3c are provided in the furnace external spaces S3a to S3c, respectively. Pressure sensors 62a to 62c for measuring the atmospheric pressure in the furnace internal space are provided in the furnace internal space of the slow cooling furnace 50 surrounded by the furnace wall 12a at the same position in the height direction of the pressure sensors 47a to 47c (FIG. 10).
In this modification, the pressure sensors 60 and 62a to 62c are provided at each position in the furnace internal space. However, pressure measurement may be performed by inserting a pressure sensor at each position in the furnace internal space. .

  In addition, outside the partition walls separating the furnace outside spaces S1, S2, S3a to S3c and the space S4, the fans 52, 53, 54a, and the fans S1, S2, S3a to S3c and the space S4, respectively. 54b, 54c, and 55 are provided. The air sent from the atmosphere by the blowers 52, 53, 54a, 54b, 54c, 55 is supplied to the furnace external spaces S1, S2, S3a to S3c and the space S4 through the pipes. The amount of air sent by the blowers 52, 53, 54a, 54b, 54c, 55 is determined by a drive signal from a drive unit 72 (see FIG. 11) described later.

FIG. 11 is a diagram illustrating a control system that controls the amount of air that the blowers 52, 53, 54a, 54b, 54c, and 55 send in.
The control system includes pressure sensors 60, 62a to 62c provided in the furnace internal space, pressure sensors 45, 46, 47a to 47c, 48 provided in the furnace external space, a control device 70, and a drive unit 72. And blowers 52, 53, 54a, 54b, 54c, and 55.
The control device 70 includes a measurement result of atmospheric pressure in the furnace internal space sent from each of the pressure sensors 60, 62a to 62c, and a measurement result of atmospheric pressure in the external space of the furnace sent from the pressure sensors 45, 46, 47a to 47c, 48. Is used to adjust the difference in air pressure at the same position in the height direction in the furnace inner space and the furnace outer space to the set range, so that the air sent by the blowers 52, 53, 54a, 54b, 54c, 55 A control signal for adjusting the amount is generated. The generated control signal is sent to the drive unit 72.
The drive unit 72 generates a drive signal for individually adjusting the amount of air sent by the blowers 52, 53, 54a, 54b, 54c, 55 based on the control signal. The drive unit 72 sends drive signals to the fans 52, 53, 54a, 54b, 54c, and 55, respectively.
In this modification, the control device 70 and the drive unit 72 automatically control the air feed amount, but the operator may manually adjust the air feed amount.

Here, the amount of air sent from the blowers 52, 53, 54a, 54b, 54c, 55 is such that the pressure in the furnace outer space S2, S3a to S3c is lower than the pressure in the furnace inner space at the same position in the height direction. Thus, the atmospheric pressure in each furnace external space is adjusted. That is, the atmospheric pressure is controlled such that the atmospheric pressure inside the furnace chamber, which is the furnace internal space, becomes larger than the atmospheric pressure outside the furnace chamber, which is the external space of the furnace.
The difference in the atmospheric pressure obtained by subtracting the atmospheric pressure in the furnace external space S2 from the atmospheric pressure in the furnace internal space of the molding furnace 80 is more than 0 to 40 Pa, preferably 4 to 35 Pa, more preferably 8 to 30 Pa, More preferably, it is 10-27 Pa, and more preferably 10-25 Pa. When the difference in the atmospheric pressure exceeds the above range, a large amount of air may flow out from the gap between the furnace walls from the furnace inner space toward the furnace outer space S2, and the air in the furnace inner space is accompanied by the outflow of this air. Increase the rise of. On the other hand, when the difference in the atmospheric pressure is below the above range, air may flow from the furnace wall space toward the furnace internal space from the furnace wall space S2. This rise in air and the inflow of air causes the temperature distribution in the furnace interior to vary. By adjusting the difference in the atmospheric pressure to the above range, it is possible to prevent the air from rising or flowing in. For this reason, the dispersion | variation in the temperature of furnace interior space can be suppressed. Thereby, the dispersion | variation in the cooling rate of strip | belt-shaped glass and by extension, plate | board thickness deviation of strip | belt-shaped glass can be suppressed. In this case, it is preferable that the pressure in the outer space of the furnace is higher as the position in the height direction is higher. Thereby, since the magnitude | size of the upward airflow which generate | occur | produces along a furnace wall can be reduced in a furnace exterior space, the dispersion | variation in the temperature of a furnace interior space can also be suppressed by extension.
Moreover, the difference in atmospheric pressure between the furnace internal space of the slow cooling furnace 50 and the furnace external space S3a to S3c is more than 0 to 40 Pa, preferably 2 to 35 Pa, more preferably 2 to 25 Pa, It is more preferably 3 to 23 Pa, and further preferably 5 to 20 Pa. When the difference in the atmospheric pressure exceeds the above range, a large amount of air may flow out of the gap between the furnace walls from the furnace inner space toward the furnace outer space S3a to S3c, increasing the rise of air in the furnace inner space. . On the other hand, if the difference in the atmospheric pressure is below the above range, air may flow from the furnace outer space S3a to S3c toward the furnace inner space through the gap in the furnace wall. As a result, the temperature distribution in the furnace internal space varies. By adjusting the difference in atmospheric pressure within the above range, air rise and air inflow can be prevented, so that variations in the temperature of the internal space of the slow cooling furnace 50 can be suppressed. Thereby, the deformation | transformation of a strip | belt-shaped glass, a curvature, the dispersion | variation in a plane distortion, and the dispersion | variation in heat shrink can be suppressed.
As described above, in the present modification, the amount of air fed into the blower is controlled so that the air pressure in the furnace internal space (furnace chamber) is larger than the air pressure in the furnace external space (outside the furnace chamber). The flow of low-temperature air can be suppressed in the furnace internal space. As a result, temperature fluctuations in the furnace internal space can be suppressed. Therefore, it is possible to suppress the thickness deviation of the strip-shaped glass and further the glass substrate.

(Modification 5)
In the present embodiment, among the members constituting the upper space in the molding furnace, the member facing the molded body 14 (molten glass), for example, the member of the furnace wall 12a (see FIG. 3A) or the furnace wall 12a If a variation in temperature distribution or variation in emissivity occurs in the surface member facing the upper space, the temperature distribution of the molten glass in contact with the molded body 14 also varies, and as a result, a strip glass and a glass substrate. Thickness deviation occurs. In this modification, the thermal conductivity is 25 to 200 W / m · K and the emissivity is 0.8 on the member facing the molded body 14 (molten glass) among the members constituting the upper space in the molding furnace. A material of ~ 1 is used. The material (for example, SiC etc.) similar to the said frame member 18a etc. is applicable to the member which faces the molded object 14 (molten glass) among the members which comprise the upper space in a shaping | molding furnace. Moreover, the thickness deviation of the member facing the molded body 14 (molten glass) among the members constituting the upper space in the molding furnace is 5 mm or more, thereby further suppressing the thickness deviation of the strip glass and the glass substrate. can do.

(Modification 6)
Among the members constituting the lower space in the molding furnace, if the temperature distribution variation or emissivity variation occurs in the member facing the band glass, the temperature distribution of the band glass also varies, and as a result Thickness deviation will occur in the glass and glass substrate. Therefore, among members constituting the lower space in the forming furnace, a member facing the glass ribbon, for example, a member of the furnace wall 12a (see FIG. 3A) or a surface member facing the lower space of the furnace wall 12a is heated. It is preferable to use a material having a conductivity of 25 to 200 W / m · K and an emissivity of 0.8 to 1. The material (for example, SiC etc.) similar to the said frame member 18a etc. can be applied to the member which faces strip | belt-shaped glass among the members which comprise the lower space in a shaping | molding furnace, for example. In addition, among the members constituting the lower space in the forming furnace, the thickness of the member facing the strip glass is set to 5 mm or more, so that the thickness deviation of the strip glass and the glass substrate can be further suppressed. .

(Modification 7)
When a glass substrate is manufactured by the overflow down draw method, a rising air flow is generated from the downstream side to the upstream side of the strip glass due to the chimney effect in which the moving path of the strip glass extending in the vertical direction of the glass manufacturing apparatus 10 is an elongated space. Sometimes. The temperature of the ascending airflow is often lower than that of the molten glass or the band-shaped glass, and the temperature distribution of the band-shaped glass varies due to the difference in the flow rate of the ascending airflow or the temperature difference of the ascending airflow in the region in the glass manufacturing apparatus 10. It is assumed that plate thickness deviation of the strip glass and the glass substrate occurs. In this modification, by minimizing the passage of the updraft and making the width of the moving path uniform, temperature fluctuations in each region in the furnace chamber 12 due to the influence of the updraft can be suppressed, and thus It can suppress that dispersion | variation arises in the temperature distribution of a strip glass and a glass substrate.
In this modification, the width of the slit-shaped gap 19 (see FIG. 3A) for guiding the glass strip formed by the molded body 14 to the lower space where the roller 16 is located, formed by the heat insulating plate 18 (see FIG. 3A). 18) is preferably 30 mm to 140 mm, and more preferably 40 mm to 100 mm. In addition, although the said clearance gap 19 can suppress that the said updraft flows into upper space, so that the clearance gap is narrow, when the width | variety of the clearance gap 19 becomes narrow too much, it will be said that strip | belt-shaped glass touches and gets on. Problems may arise. For this reason, the width of the slit-shaped gap 19 is preferably 30 mm or more.

[Examples and conventional examples]
In order to investigate the effect of this embodiment, a strip glass was manufactured using the conventional heat insulation plate (conventional example) and the heat insulation plate of this embodiment (example), and the variation in the thickness of the strip glass was measured. .
The glass substrate manufacturing apparatus used is a glass manufacturing apparatus 10 based on the overflow downdraw method, which is one of the downdraw methods shown in FIG. As the glass, aluminosilicate glass (glass substrate for liquid crystal display) having the following composition was used, and the molten glass was molded in a molten state at 1300 ° C. For this reason, the temperature atmosphere of the upper space where the molded body 14 is located was adjusted to 1300 ° C. On the other hand, the temperature atmosphere in the lower space was adjusted to 600 ° C. The width of the strip glass was 2 m, and the roller 16 was pulled to form a strip glass having a thickness of 0.7 mm. The distance between the band-shaped glass surface and the opposing surface of the heat insulating plate 18 was 50 mm.

(Glass composition)
SiO ₂ : 60% by mass
Al ₂ O ₃ : 19.5% by mass
B ₂ O ₃ : 10% by mass
CaO: 5% by mass
SrO: 5% by mass
SnO ₂ : 0.5% by mass.

As shown in FIG. 12, the conventional heat insulating plate, which is a conventional example, was formed by connecting three ceramic fiber boards 24a to form an integrated heat insulating plate 24 having a width of 2 m. Accordingly, there are two seams on the facing surface 24a of the heat insulating plate 24 facing the belt-like glass.
On the other hand, as shown in FIGS. 4A and 4B, the heat insulating plate 18 of the present embodiment as an example is a hollow rectangular column made of SiC so as to surround the ceramic fiber boards 18e to 18g. A frame was made using the frame members 18a to 18d. Each of the frame members 18a to 18d has a square shape with a side of 60 mm, and the thickness of the frame members 18a to 18d is 7 mm. Each member of the frame members 18a to 18d was mechanically joined by providing metal plates at four corners. Further, the frame members 18a to 18d were provided with L-shaped metal plates for preventing the ceramic fiber board from falling off using holes formed in the side surface of the frame at a pitch of about 300 mm. The hollow portions of the frame members 18a to 18d were filled with alumina fibers as a heat insulating material. In this frame, as shown in FIG. 4A, three ceramic fiber boards 18e to 18g, which are heat insulating materials, were provided without gaps.

The thermal conductivity at an upper space temperature (1300 ° C.) of the frame member 18a of the heat insulating plate 18 according to the example is about 45 W / m · K, the bubble content is about 0.6%, and the emissivity is 0.00. 95. In addition, the thermal conductivity at the upper space temperature (1300 ° C.) of the ceramic fiber board which is a heat insulating material is about 0.2 W / m · K, the bubble content is 45%, and the emissivity is about 0.6. there were. The heat resistance of the heat insulating plate 18 was 0.25 m ² · K / W.
On the other hand, the thermal conductivity at the upper space temperature (1300 ° C.) of the conventional heat insulating plate 24, which is a conventional example, is 0.23 W / m · K, the bubble content is 45%, and the emissivity is about 0.00. 6. The heat resistance of the heat insulating plate 24 was 0.22 m ² · K / W.
The thermal conductivity was measured by a test method (JIS R 1611-1997) for thermal conductivity of fine ceramics by a laser flash method. The bubble content was calculated by {1- (bulk density / true density) × 100}. The thermal resistance was calculated according to thermal resistance = thickness / thermal conductivity. The emissivity was measured with a radiation thermometer.

After producing strip glass (liquid crystal display glass substrate) for two months using the two heat insulating plates 18 and 24, the thickness of the strip glass (liquid crystal display glass substrate) is measured using a micrometer. Measurements were made to obtain a thickness distribution.
When the heat insulating plate 24 which is the conventional example was used, the thickness deviation, that is, the plate thickness deviation was 30 μm within the effective width (width cut out as a product) of the strip glass (liquid crystal display glass substrate). In other words, the thickness deviation cannot be suppressed to 25 μm or less, and within the effective width of the band-like glass (liquid crystal display glass substrate), a relatively small period of thickness irregularity of about 3 μm along the width direction. occured. On the other hand, when the heat insulating plate 18 which is the embodiment shown in FIGS. 4A and 4B is used, the uneven thickness of the short period does not occur, and within the effective width of the band-like glass (liquid crystal display glass substrate), The thickness deviation was 12 μm. That is, it has been found that the thickness deviation can be suppressed to 20 μm or less, and the strip glass (glass substrate for liquid crystal display) can be stably produced.
Further, even when the heat insulating plate 18 was used, no contraction in the width direction of the strip glass due to insufficient cooling at both ends of the strip glass in the lower space of the furnace chamber 12 was not observed. That is, even when the heat insulating plate 18 is used, it was found that the heat insulating effect in the upper space and the lower space of the furnace chamber 12 is sufficient.

When the heat insulation board 24 (conventional example) used for two months was taken out and the shape change was confirmed, in the heat insulation board 24 with a width of 2.5 m, the central part is warped 5 mm convexly toward the lower space. confirmed. On the other hand, the “warp” of the heat insulating plate 18 (Example) when taken out of the furnace was less than 1 mm.
As mentioned above, the effect of this embodiment is clear.

  As mentioned above, although the manufacturing apparatus of the glass substrate and the manufacturing method of the glass substrate of this invention were demonstrated in detail, this invention is not limited to the said embodiment, In the range which does not deviate from the main point of this invention, various improvement and a change are carried out. Of course.

The glass manufacturing apparatus 10 of this embodiment is suitably applied to manufacture of a glass substrate for a liquid crystal display or a glass substrate for a display cover glass, for example.
The heat insulating plate 18 used in the glass manufacturing apparatus 10 is suitable for a heat insulating plate installed in the very vicinity of the molded body 14. However, the present invention is not limited to this, and a plate similar to the heat insulating plate 18 can be applied to a heat insulating plate provided downstream of the heat insulating plate 18 installed in the very vicinity of the molded body 14. is there.

DESCRIPTION OF SYMBOLS 1 Melting apparatus 1a Melting tank 1b Clarification tank 1c Stirring tank 1d, 1e Pipe 6 Molding apparatus 8 Cutting apparatus 10 Glass manufacturing apparatus 12 Furnace chamber 12a Furnace wall 14,114 Molded body 14a Groove 14b, 14c Wall surface 14d Bottom end 16 Roller 18, 118 Insulating plates 18a, 18b, 18c, 18d Frame members 18e, 18f, 18g Ceramic fiber board 18h Insulating body 18i, 20 Members 18j, 18k, 18m, 18n, 22 Insulating material 19 Clearance 20 Member 23 Tube 24 Insulating plate 24a Opposite Surface 30 Cooling units 32a, 32b, 32c, 32d, 32e, 32f, 32g, 32h Transport rollers 41, 42, 43a, 43b, 43c, 44 Floor surface 45, 47a, 47b, 47c, 48 Pressure sensor 50 Slow cooling furnace 52, 53 , 54a, 54b, 54c, 55 Blower 60, 62a 62b, 62c the pressure sensor 70 control unit 72 drive unit 80 forming furnace

Claims (7)

A glass substrate manufacturing apparatus for manufacturing a glass substrate from molten glass using a downdraw method,
A furnace chamber surrounded by a furnace wall;
A molded body provided in the furnace chamber for molding a strip glass from molten glass;
A roller provided in the furnace chamber;
A heat insulating plate including a heat insulating material that partitions the molded body and the roller into two different spaces, and
In the furnace chamber, a slit-like gap is formed by the heat insulating plate to guide the glass strip formed from the molded body to the space where the roller is located.
In the gap, at least on the facing surface of the heat insulating plate facing the belt-like glass, a second material having a lower bubble content than the first material used for the heat insulating material (however, containing bubbles) The glass substrate manufacturing apparatus is characterized in that the rate is excluding 0%) . When manufacturing glass substrates from molten glass by the downdraw method,
Forming two molten glass streams on opposite wall surfaces of a molded body provided in a furnace chamber surrounded by the furnace wall;
Passing through a slit-shaped gap formed by a heat insulating plate including a heat insulating material, which divides the furnace chamber into a glass strip formed by joining two molten glass flows, and
In the step of passing through the gap, in the gap through which the strip glass passes, the opposed surface of the heat insulating plate facing the strip glass has a bubble content compared to the bubble content of the first material used for the heat insulating material. A second material having a low air content (however, the bubble content is excluding 0%), and the opposed surface gives a substantially uniform heat distribution in the width direction of the belt-like glass. A method for producing a glass substrate. The method for manufacturing a glass substrate according to claim 2 , wherein the thermal conductivity of the second material is higher than the thermal conductivity of the first material. The facing surface of said insulating plate is a side of the hollow prismatic member, the hollow portion of the prism member, wherein the first material is filled, the glass substrate according to claim 2 or 3 Manufacturing method . The thermal resistance of the said heat insulation board is a manufacturing method of the glass substrate of any one of Claims 2-4 which is 0.2 m < ² > * K / W or more. The manufacturing method of the glass substrate of any one of Claims 2-5 which manufactures the glass substrate whose width | variety of the width direction is a magnitude | size of 2000 mm or more. The method for manufacturing a glass substrate according to any one of claims 2 to 6 , wherein the pressure outside the furnace chamber is higher as the position in the height direction is higher .

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